Add EasyEDA Std project source ingestion (10 boards backfilled)

打通 oshwhub origin=std 项目的工程源（schematic + PCB dataStr）抓取链路。原
plan.md §1.6 假设需要登录，实测 lceda.cn/api/documents/<doc>?uuid=<doc>&path=<doc>
对公开项目匿名可访问 —— 无需 cookie，无账号封禁风险。

调研：4 轮探测留痕在 data/state/std_probe[1-5]/（gitignored）；翻 Std 编辑器
v6.5.51 的 main.min.js bundle 找到 ajaxDetail 端点；按 docType 区分两种
响应 shape（schematic 项目视图 vs PCB 文档视图）。

Crawler:
  - make_source_client() 用浏览器 UA + lceda.cn/editor Referer，因为
    oshwhub /api/project/<uuid> 端点拒绝 FacereDataset/0.1 UA（CLAUDE.md
    UA 例外条款：目标站主动封自定义 UA + 公开静态资源）
  - fetch_std_source(): 项目元 → version_documents → 逐文档 dataStr → 落
    source/<doc>.json + source/manifest.json
  - --with-source（爬新项目时一并抓源）/ --backfill-source（仅扫已有）
  - QPS ≤ 0.2 (SLEEP_SOURCE = 5s) 自律

Schema: 加 source_format / source_path / source_documents / editor_version
（前 3 进 enum 锁定，便于后续 Pro / KiCad 源对齐）。

回填结果：10/10 成功，45 个文档，33.2 MB；schema validate 全通。
docTypes 主要是 1 (schematic) 与 3 (pcb)；USB 电压电流表只有 PCB 文档（4 个：
主板+盖板+底板+面板，作者未上传原理图源）。

完整调研：docs/sources/easyeda_std_source.md。

data/raw/oshwhub/7b6a398811f14eba9a952b8d2ddd7ace/metadata.json

@@ -81,5 +81,58 @@
     "public": true,
     "publish": true,
     "skipped_files": []
-  }
+  },
+  "source_format": "easyeda-std",
+  "source_path": "source/",
+  "source_documents": [
+    {
+      "doc_uuid": "93adc47efbde48a28807aa0f0bd01b91",
+      "docType": 3,
+      "master": "9bce7682b0d24831b41fae252149903b",
+      "path": "source/93adc47efbde48a28807aa0f0bd01b91.json",
+      "size": 494518,
+      "sha256": "05abeda96d3a555838a3297d91e9ea31848f083f53aee7d6788007e8f22538e4"
+    },
+    {
+      "doc_uuid": "f47314d9558c4171aa33c8e17a0f2b80",
+      "docType": 3,
+      "master": "a2c0244bd519418da78c50f187466114",
+      "path": "source/f47314d9558c4171aa33c8e17a0f2b80.json",
+      "size": 1225471,
+      "sha256": "078b20cc90b202a9651f8404c6b3dffa8a605feae9076703a7da725ce4817943"
+    },
+    {
+      "doc_uuid": "d0cbe19ba8fb4ba6827512bf424f019e",
+      "docType": 3,
+      "master": "abb4c0da30864fa5b23ea0ae2066b50a",
+      "path": "source/d0cbe19ba8fb4ba6827512bf424f019e.json",
+      "size": 494463,
+      "sha256": "eb8b801d737d27eefc5eb275c20c86948392b0d030e4ed70d3e2f266d5df3b27"
+    },
+    {
+      "doc_uuid": "6474b2b8414f4594a73f5c675fec151e",
+      "docType": 1,
+      "master": "1f66702c7edb4dbf851c4e8bf96efed9",
+      "path": "source/6474b2b8414f4594a73f5c675fec151e.json",
+      "size": 4452301,
+      "sha256": "67d55a49d705403e24dd461a3ec940f06f4e98203f201f74df45d5334f441792"
+    },
+    {
+      "doc_uuid": "40613f5bc09746c8858f02ebbd3c0c0c",
+      "docType": 3,
+      "master": "a0ceddef86c1471788332d86e5c6a750",
+      "path": "source/40613f5bc09746c8858f02ebbd3c0c0c.json",
+      "size": 1173475,
+      "sha256": "738e194ebb348b294b1ecbc436afadfbb79a7336b80a594eb880b6fa0bcd484f"
+    },
+    {
+      "doc_uuid": "7ea961c70bc54ecebe075ebc8fb0051b",
+      "docType": 1,
+      "master": "1440abb8f989434794306e445f2a3ba7",
+      "path": "source/7ea961c70bc54ecebe075ebc8fb0051b.json",
+      "size": 4452301,
+      "sha256": "67d55a49d705403e24dd461a3ec940f06f4e98203f201f74df45d5334f441792"
+    }
+  ],
+  "editor_version": "6.5.43"
 }